A drum-type weft measuring and storing device winds a length of weft yarn longer than that required for one picking cycle on a measuring and storing drum, and restrains or releases the weft yarn wound on the measuring and storing drum by controlling a restraining pin disposed adjacent to the circumference of the measuring and storing drum so as to be advanced and retracted. In one cycle of the weaving operation of the loom, the retraction of the restraining pin, hence the release of the weft yarn, is phased with pick starting timing, while the advancement of the restraining pin, hence the restraint of the weft yarn, corresponds directly with the control of the length of the weft to be unwound in one picking cycle.
Conventionally, the restraining pin is controlled for advancement and retraction by a cam mechanism or the like in synchronism with the weaving operation of the loom. Accordingly, the weft release timing always coincides with a fixed crankshaft angle of the loom.
However, the variation of the baloon of the weft yarn or of resistance against the movement of the weft yarn during unwinding of the weft yarn from the measuring and storing drum due to the variation of the outside diameter of the weft feed package or other causes the variation of the crankshaft angle of arrival of the picked weft yarn at the arrival position on the opposite side of the loom and hence the variation of the traveling speed of the weft yarn. If the restraining pin advancing crankshaft angle is fixed irrespective of the variation of the traveling speed of the weft yarn, the weft yarn measuring and storing device is unable to supply a fixed length of the weft yarn for picking operation, and thereby an excessive or insufficient length of the weft yarn is inserted. Consequently, normal picking operation control is impossible. The same problem occurs with other picking operation control member, namely, the picking nozzle.
On the other hand, the present invention is an improvement of an invention disclosed in Japanese Patent Laid-open Publication No. 60-259,652. This prior invention detects the actual crankshaft angle of arrival of the weft yarn at the final arrival position on the weft yarn receiving side, namely, the side opposite the picking side, of the loom. Accordingly, the system of the prior invention is susceptible to the vibration of the free end of the weft yarn and fly, and is liable to malfunction frequently. Furthrmore, since this system measures the actual crankshaft angle of arrival of the weft yarn after the completion of the picking operation, and then starts computation for determining control data, the control operation is delayed, and hence the system is incapable of rapid control operation.